A Research On Nonlinear Effect Supression Of Optical Fiber Communication By Optical Phase Conjugation

With the rapid development of optical fiber communication,systems with longer transmission distance,higher transmission bitrate and larger transmission bandwidth are urgently needed,but the existence of fiber dispersion and nonlinearity in optical transmission hinders people from moving further,higher and faster targets advance,so the suppression of fiber dispersion and nonlinear effects in optical transmission is of particular concern.Optical Phase Conjugation(OPC)not only theoretically completely suppresses the Kerr nonlinear effect of the fiber,but also compensates for the even-order dispersion of the fiber.On the other hand,for the reason that there is no photoelectric conversion and electro-optic conversion in the transmission,thereby reducing energy loss,OPC has been widely concerned.Starting from the Maxwell's equations,this thesis solves the wave equation through the Maxwell's equations,and then deduces the Nonlinear Schr?dinger Equation which is used to explain the suppression of nonlinear effects of OPC on the fiber from the wave equation in detail.For the structure of the OPC model,the conversion efficiency of the Four-wave Mixing(FWM)is studied in detail.In the first,the expression of FWM conversion efficiency is derived in theory,and at the same time,the key factors which affect the conversion efficiency of FWM are found by the expression of FWM conversion efficiency.Second,the FWM simulation system is built through the simulation software and then the FWM process is demonstrated to simulate the maximum conversion efficiency of the FWM under different conditions.At last,the FWM experimental system is built to verify the simulation results.Aim at the mitigation of the nonlinear effect on optical fiber communication system by OPC,this thesis studies the degree of suppression of single channel system and Wavelength Division Multiplexing system,respectively.Firstly,the SNR of single channel communication system modulated by QPSK with OPC model is derived by formula,and the theoretical maximum Q value is calculated simultaneously.After that,for the single channel optical communication system modulated by QPSK,the transmission experimental verification based on a bitrate of 10 Gbit/s and a transmission distance of 50 km is carried out.The experimental results are basically consistent with the theoretical results,which shows that OPC can effectively suppress fiber nonlinearity in the optical transmission thus improving system performance.Finally,through the simulation software,the simulation system is built,comparing the suppression effect of single channel and WDM optical communication systems of OPC on the nonlinear effect of fiber from the aspects of launch power,transmission bitrate,transmission distance and modulation format.The simulation results show that,the communication system with OPC model not only improves the signal quality at the receiver,but also increases the maximum launch power threshold at the transmitter.